Certain characteristics are common to all Communication Disorders. First, the diagnostic criteria for each require that the disorder must not be caused by intellectual disabilities or a neurological disorder (such as epilepsy, for example). In all Communication Disorders, a child's communication ability resembles that of a much younger child, which creates problems at school, at home and with peers (particularly in school). These disorders may run in families (e.g., there may be a genetic component to some communication disorders). They are more frequently diagnosed in boys than in girls and are more common among younger children than older children. Although the characteristics described above are common among all Communication disorders, there are also a wide range of subtypes and varying levels of severity among these disorders.

Expressive Language Disorder

Children with Expressive Language Disorder have difficulties with speech and vocabulary and have word finding problems. As a result, they speak using simplified sentences.

Symptoms of Expressive Language Disorder include:

Problems recalling words

Limited vocabulary

Frequent errors in correctly producing the proper tense of words (e.g., using "goes" instead of "went" for past tense)

Difficulty finding a proper or desired word to use in a sentence

Difficulty with producing sentences appropriate in length and complexity for the child's age

According to the DSM, an Expressive Language Disorder is diagnosed when children's scores on tests of expressive language (i.e, speaking and communicating verbally) are significantly lower than their scores on tests of nonverbal intellectual ability (e.g., pattern matching) and receptive language development (i.e., ability to understand spoken language).

Phonological Disorder

A Phonological Disorder occurs when a child fails to use speech sounds that are appropriate for their age, dialect, and developmental level. For example, a child with Phonological Disorder might substitute one sound for another (like using the "t" sound when trying to make a "k" sound), or omit consonant sounds at the ends of a word.

Symptoms of Phonological Disorder include:

Developmental delays in speech sound production

Age-inappropriate difficulty with regard to articulation and expression

Making sound substitutions or omissions (e.g., use of /t/ sound for /k/)

Often, the child affected by the disorder does not show any other language or comprehension problems, but may have some symptoms similar to those of Expressive Language Disorder (e.g., the child may produce errors in selection of proper verb tense or have difficulty producing age-appropriate complex sentences).

Mixed Receptive-Expressive Language Disorder

This disorder occurs when a child has problems both in understanding and expressing language. Children with this disorder display symptoms consistent with expressive language disorders, and also have difficulty understanding words, sentences, or certain types of words (e.g., such as words related to time, such as "hours, minutes, days" or "when, now, later"). This mixed language disorder is often a prelude to later significant learning problems because of how difficult it is to learn when you can't understand or communicate easily with teachers and peers.

Children demonstrating symptoms of Mixed-Receptive Language Disorder may sometimes appear to be deaf or inattentive, and they may have problems understanding and/or following with verbal directions. They may also have memory or sequencing difficulties (i.e., problems understanding directions, or problems remembering which direction in a set of directions to execute first).

According to the DSM, a Mixed-Receptive Language Disorder is diagnosed when children's receptive and expressive language test scores are both significantly lower than their scores on tests of nonverbal intellectual abilities. The mixed language difficulties must not be better accounted for by a Pervasive Developmental Disorder (a PPD) such as Autism or Asperger's Disorder which also manifest as difficulties with social interactions, language and communication.